The large-scale high-speed landslide has a strong destructive power which seriously threatens human lives and belongings. In order to study the dynamic process of large-scale high-speed landslide disasters and find the causes, the back analysis is made to study the Frank slide, a typical large-scale high-speed landslide disaster which happened in Canada, by combining dynamic model equation and method of finite volume discretization. At the same time, the simulation realizes the reappearance of the dynamic process of large-scale high-speed landslide disasters. It is can be seen from the calculation results which are identical to the actual situation that the established theoretical model and the numerical solution are effective. Besides, the low bottom friction parameter obtained from the back analysis shows that the decrease of the friction resistance is one of the most important causes of large-scale high-speed landslide. The further analysis reveals that several factors such as high-speed motion, fluid pressure on the sliding surface and high normal stress can reduce the friction resistance on the sliding surface.